The present invention relates to improvements in changeable signs. One of the inventors of this application, Fred M. Black, is the inventor of U.S. Pat. No. 4,761,905 entitled "Scanned Electromechanical Display" and U.S. Pat. No. 4,912,442 entitled "Scanned Electromechanical Alphanumeric Display". The disclosures of both these patents are hereby specifically incorporated herein by reference. The present invention relates to improvements on the changeable sign disclosed in those patents. The patents disclose sign elements which can display alphanumeric or graphic images on a pixel-by-pixel basis, generally arranged in a rectangular grid. The pixels are made up of solid elements having multiple sides of contrasting appearances, so that the display of one side or the other is noticeable. The overall pattern made up by the collection of pixel elements makes a perceived image, whether of an alphanumeric character, a graphic image, or the like. The prior patents disclosed arrays of such pixel elements and devices which pass behind the arrays to pivot the pixel elements to selectively display one or the other of the contrasting sides. The present invention has that notion in common, but provides improved design features to reduce the cost, enhance the picture quality, and enhance the reliability of the sign.
One of the important elements in making signs of this type is to provide as large as possible a mark-to-space ratio. That is, for each perceptible pixel size, as much as possible of the size should be displayed as the mark or distinctive appearance rather than an unchanging border. The present invention provides features which enhance the mark-to-space ratio over the prior art.
These features were not provided by the prior art, therefore leaving a need for improvements.